This invention relates to lance tips for oxygen steelmaking and is particularly concerned with an improvement in cooling the distal end of a tip.
Numerous constructions for oxygen lance tips are known in the art. Examples of these lance tips are shown in the following U.S. Pat. Nos.: 2,979,270; 3,118,608; 3,170,016; 3,201,104; 3,302,882; 3,304,009; 3,309,195; 3,322,419; 3,337,203; 3,385,587; 3,427,151; 3,662,447; 3,752,402; 3,797,814; 3,052,005; 4,190,238; and 4,301,969.
An oxygen lance, particularly the lance tip, must be of extremely rugged construction due to the extreme conditions to which it is subjected when put to use by being exposed to the high temperatures and reactive materials within the interior of a steelmaking vessel. Out of necessity coolant passages through which coolant is conducted are provided for the lance tip so that the tip can survive its use in the high temperature metallurgical process.
It has been the practice in the art often to provide drilled holes in the tip head through which coolant is conducted. Examples of typical constructions are shown in many of the aforementioned patents. It is also known to provide a central inlet coolant passage extending through the tip head stopping short of the distal end face with generally radially extending passages intercepting the central passage adjacent the distal end face and conducting coolant radially from the central passage across the distal end of the tip to the outer perimeter of the tip where the coolant exits via a return passage back through the tip and the lance. The objective of this type of construction is to increase the cooling effect of the distal end of the tip where the conditions are particularly severe by maximizing the coolant flow across the end face of the tip. Because oxygen passages also extend through the tip to discharge oxygen at locations in the distal end of the tip, it is impossible for the radial coolant passages to cover the full extent of the distal end surface area. Because of structural considerations it is also necessary that certain wall thicknesses be provided between the radial coolant passages and the generally axially extending oxygen passages, and this reduces the amount of surface area which can be exposed to coolant. Furthermore, while it is desirable to place the radial passages as close to the distal end of the tip as possible, once again structural consideration can limit the proixmity, and this also reduces the cooling efficiency.
The coolant passages in prior tips possess the disadvantage of restricting the coolant flow without adequately utilizing the high coolant velocities thereby obtained. Inadequate control of coolant flow pattern and distribution of coolant flow have resulted in early deterioration of the lance tip.
Accordingly, with prior tip constructions, a point is eventually reached where the erosion or deformation of the tip mandates replacement of the tip. The cost of replacing a tip is substantial. Extension of the useful life of a tip can therefore improve the oxygen steelmaking process by contributing to a reduction in operating costs.
The present invention is directed to a new and improved oxygen lance tip with particular improvement being made to the cooling of the distal end face of the tip. With the improvement of the present invention the useful life of an oxygen lance tip can be significantly extended thereby contributing to reduction in operating costs at an oxygen steelmaking facility. A lance tip embodying principles of the invention provides coolant flow across the end face of the tip which is carefully controlled with regard to velocity and distribution. The tip is structurally very strong so as to resist and minimize the thermal and mechanical stresses.